The invention finds highly significant applications in the field of mobile radio used in cellular networks of the GSM, AMPS, ETACS, etc. . . . type. In modern networks, the passband used is relatively large. As the apparatus used is portable, the dimensions are desired to be small, which imposes on the antennas the necessity of also being as compact as possible, particularly when the apparatus is in the standby mode for a communication. The antennas are in that case put in their retracted position. One is thus confronted with the problem that a wideband operation is to be harmonized with compactness of the antennas. It should be recollected that there are problems when compact antennas are to operate with a wide band.
An apparatus formed by such an antenna device is known from European patent document No. 0 644 606.
This antenna has the drawback that, in retracted position, the wire continues to be connected to the excitation device and, when the apparatus is in the transmit mode, radiates energy inside the apparatus which may be annoying to circuits which receive the radiated wave and also annoying for wave reception when the apparatus is in the receive mode.